Updating LVGL Library

How-to
1

Hello all,
I have a simple Hello World working on a LVGL 8.3.8 version.
When I try to update the Library to the newest (9.1.0), I get several errors from undefined functions and variables. Seems a lot of the API changed.
Unfortunately, I haven’t been able to get a Hello World working on the newest version, and the examples / demos are made in the 8.2.0 (i.e.: GitHub - lvgl/lv_platformio: PlatformIO project example for LVGL ).

This is the working 8.3.8 Hello World:

#include <lvgl.h>
#include <TFT_eSPI.h>

static const uint16_t screenWidth  = 240;
static const uint16_t screenHeight = 240;

static lv_disp_draw_buf_t draw_buf;
static lv_color_t buf[ screenWidth * screenHeight / 10 ];

TFT_eSPI tft = TFT_eSPI(screenWidth, screenHeight); /* TFT instance */

#if LV_USE_LOG != 0
/* Serial debugging */
void my_print(const char * buf)
{
    Serial.printf(buf);
    Serial.flush();
}
#endif

/* Display flushing */
void my_disp_flush( lv_disp_drv_t *disp_drv, const lv_area_t *area, lv_color_t *color_p )
{
    uint32_t w = ( area->x2 - area->x1 + 1 );
    uint32_t h = ( area->y2 - area->y1 + 1 );

    tft.startWrite();
    tft.setAddrWindow( area->x1, area->y1, w, h );
    tft.pushColors( ( uint16_t * )&color_p->full, w * h, true );
    tft.endWrite();

    lv_disp_flush_ready( disp_drv );
}


void setup()
{
    Serial.begin( 115200 ); /* prepare for possible serial debug */

    String LVGL_Arduino = "Hello Arduino! ";
    LVGL_Arduino += String('V') + lv_version_major() + "." + lv_version_minor() + "." + lv_version_patch();

    Serial.println( LVGL_Arduino );
    Serial.println( "I am LVGL_Arduino" );

    lv_init();

#if LV_USE_LOG != 0
    lv_log_register_print_cb( my_print ); /* register print function for debugging */
#endif

    tft.begin();          /* TFT init */
    tft.setRotation( 0 ); /* Landscape orientation, flipped */

    lv_disp_draw_buf_init( &draw_buf, buf, NULL, screenWidth * screenHeight / 10 );

    /*Initialize the display*/
    static lv_disp_drv_t disp_drv;
    lv_disp_drv_init( &disp_drv );
    /*Change the following line to your display resolution*/
    disp_drv.hor_res = screenWidth;
    disp_drv.ver_res = screenHeight;
    disp_drv.flush_cb = my_disp_flush;
    disp_drv.draw_buf = &draw_buf;
    lv_disp_drv_register( &disp_drv );

  
    /* Create simple label */
    lv_obj_t *label = lv_label_create( lv_scr_act() );
    lv_label_set_text( label, "Hello World");
    lv_label_set_recolor(label,true);
    lv_obj_align( label, LV_ALIGN_CENTER, 0, 0 );
 
     /*Or try out a demo. Don't forget to enable the demos in lv_conf.h. E.g. LV_USE_DEMOS_WIDGETS*/
    //lv_demo_widgets();
    
    Serial.println( "Setup done" );
}

void loop()
{
    lv_timer_handler(); /* let the GUI do its work */
    delay( 5 );
}
2

Are you using an ESP32?
Did you try this updated example?

3

Yes, it does not work as well, both on ArduinoIDE as well as in PlatformIO
In platformIO it’s missing an Arduino.h include, but afterwards both return the same error:

/Users/neubern/Documents/Arduino/libraries/lvgl/examples/arduino/LVGL_Arduino/LVGL_Arduino.ino: In function ‘void setup()’:
/Users/neubern/Documents/Arduino/libraries/lvgl/examples/arduino/LVGL_Arduino/LVGL_Arduino.ino:82:20: error: invalid conversion from ‘long unsigned int ()()’ to ‘lv_tick_get_cb_t’ {aka 'unsigned int ()()’} [-fpermissive]
lv_tick_set_cb(millis);
^~~~~~
In file included from /Users/neubern/Documents/Arduino/libraries/lvgl/src/…/src/misc/lv_timer.h:16,
from /Users/neubern/Documents/Arduino/libraries/lvgl/src/…/lvgl.h:31,
from /Users/neubern/Documents/Arduino/libraries/lvgl/src/lvgl.h:16,
from /Users/neubern/Documents/Arduino/libraries/lvgl/examples/arduino/LVGL_Arduino/LVGL_Arduino.ino:4:
/Users/neubern/Documents/Arduino/libraries/lvgl/src/…/src/misc/…/tick/lv_tick.h:77:38: note: initializing argument 1 of ‘void lv_tick_set_cb(lv_tick_get_cb_t)’
void lv_tick_set_cb(lv_tick_get_cb_t cb);
~~~~~~~~~~~~~~~~~^~

exit status 1

Compilation error: invalid conversion from ‘long unsigned int ()()’ to ‘lv_tick_get_cb_t’ {aka 'unsigned int ()()’} [-fpermissive]

4

That’s normal, because it is an ino file. Only the Arduino IDE will automatically add it. But this often leads to confusion.

The example is not 100% correct.

This works:

static uint32_t my_tick_get_cb(void) {
  return millis();
}

void setup() {
  ...
  lv_tick_set_cb(my_tick_get_cb);
  ...
}
1 Like